Pet store of DOOM

"PETS-R-US", used to be a peaceful place to adopt a special someone, but the place has a grim secret.

A veterinarian proclaimed MAD, had been secretly inventing a serum that changes animals into humans, and humans into animals. But as his cover was blown by police, he quickly replaced the serum animal medicines. The serum was now in animal surgeries and in the food of the workers in PETS-R-US!

Now, the workers had transformed into half-animal/half-human creatures and the animals in the shelter (and in peril), had morphed into unrecognizable humans. Police, S.W.A.T team, and Hazmat had barricaded the creatures inside so no one can get hurt or possibly get killed off.